Negative Air Ionisation

Our rating
Seasonal affective disorder 1 smiley: This treatment is promising and may be useful. It has some evidence to support it, but more evidence is needed to be sure it works.
General depression Question mark: This treatment has not been properly researched. It is not possible to say whether it is useful or not.

What is it?

A negative air ion is an atom or molecule in the air that has gained an electron, while a positive ion has lost an electron. Both positive and negative ions occur naturally in the air. However, negative ions are more concentrated in fresh air. Negative air ions can be produced by lightning, ocean surf and waterfalls. There are also electrical devices called 'air ionisers' that produce negative air ions. Such air ionisers have been used in the treatment of seasonal winter depression, or seasonal affective disorder (SAD).

How does it work?

Levels of a chemical messenger in the brain called serotonin decrease in autumn and winter. This decrease may be related to the depression that some people experience in the winter months. It has been proposed that negative air ions cause an increase in brain serotonin levels.

Is it effective?

There have been a number of well conducted studies which have looked at the effects of air ionisation on winter depression. Treatment generally involves sitting in a room with the ioniser on for 30 minutes every morning over a 2-3-week period. This type of treatment is effective in reducing depression symptoms in people with winter depression. Using a high-density ioniser is more effective than using a low-density ioniser. 

There is less evidence on the use of negative air ionisation to treat non-seasonal depression, although current evidence is promising. One study used negative air ionisation to treat people with chronic major depression, and one study has used the treatment with university students (some of whom were depressed). Both studies found that negative air ionisation reduced depression symptoms. Again, a high-density ioniser was more effective than low-density one.

Are there any disadvantages?

Air ionisers produce a very small amount of a gas called ozone, which can be harmful to humans. Air ionisers should be used in a well ventilated room to ensure that ozone levels do not build up to toxic levels.  

Where do you get it?

Air ionizers are available from electronics stores and can be bought on the internet. It is important to check the technical specifications of any air ioniser. Some of those on sale do not produce a high density of negative ions. A high-density ioniser produces 2,700,000 ions per cubic centimeter, while a low-density one produces only 10,000 ions per cubic centimeter.


Air ionisation appears to be a promising treatment for seasonal winter depression. It also appears to be a promising treatment for general depression, but more research is needed to be sure it is effective.

Key references

  • Britigan, N., Alshawa, A., & Nizkorodov, S. A. Quantification of ozone levels in indoor environments generated by ionization and ozonolysis air purifiers. J Air Waste Manag Assoc. 2006; 56(5): 601-610.
  • Flory R, Ametepe J, Bowers B. A randomized, placebo-controlled trial of bright light and high-density negative air ions for treatment of Seasonal Affective Disorder. Psychiatry Res. 2010 May 15;177(1-2):101-8.
  • Goel N, Etwaroo GR. Bright light, negative air ions and auditory stimuli produce rapid mood changes in a student population: a placebo-controlled study. Psychol Med. 2006 Sep;36(9):1253-63.
  • Goel N, Terman M, Terman JS, Macchi MM, Stewart JW. Controlled trial of bright light and negative air ions for chronic depression. Psychol Med. 2005 Jul; 35(7):945-55.
  • Terman M, Terman JS. Treatment of seasonal affective disorder with high-output negative ionizer. Journal of Alternative and Complementary Medicine 1995; 1: 87-92.
  • Terman M, Terman JS, Ross DC. A controlled trial of timed bright light and negative air ionization for treatment of winter depression. Archives of General Psychiatry 1998; 55: 875-882.

Last reviewed and updated: 1 December 2016